Sinéad O'Connor, Queen Elizabeth Hall, London

Elle for leather: Sinéad O'Connor (Marilyn Kingwill)

With her combination of vulnerability and assertiveness, anger and empathy, Sinéad O'Connor makes an apt headliner for the Southbank's Women of the World Festival. Especially since, with her new album, How About I Be Me (And You Be You)?, she's operating with a rare strength and clarity of purpose, with a band flexible enough to lend light and shade to the full range of her material.

Tonight the band is frequently required to chop out a gentle dub skank, such as that which opens the show with "The Healing Room", Sinéad striding on barefoot in a leather-look basque-and-trousers outfit topped with a piratical red bandanna, her tattoos proudly displaying her allegiances: on her right arm, a Celtic cross device; on her left arm, the Rastafarian Lion of Judah; and beneath her throat, what I take to be Jesus Christ - unless, that is, she carries some inexplicable torch for ELO mainman Jeff Lynne.

The set draws from most corners of her career, including unexpected highlights such as a moving a cappella version of "I Am Stretched on Your Grave" dedicated to PC David Rathband, and a "Never Get Old" on which the backing singers' hypnotic breaths and the droning sonorities of cello, guitars and keyboards provide a warm bed for Sinéad's keening vocal, as close as rock music gets to a muezzin wail. And of course, there's the mandatory "Nothing Compares 2 U", its power undiminished by familiarity. But the most impressive aspect of the show is the strength of new material like "The Wolf is Getting Married" and "4th And Vine", ebullient anthems in which the mutuality of love is effusively evident.

Although she admits that her shifting affections ironically meant having to change the colour of her lover's eyes in "4th And Vine" several times between its recording and eventual release. At the other emotional extreme, John Grant's vituperative "Queen of Denmark" is delivered with both barrels smoking, while her own separation song "The Last Day of Our Acquaintance" is described as the "musical version of a horseshit pizza".

Underneath the feistier assertions, however, lurks a tender sensitivity to the tribulations of those less fortunate. Tonight, it's particularly evident in the junkie apologia "Reason with Me", in which the hapless addict reasons "If I loved someone, I might lose someone". It's a heartbreaking performance: the way the bitterness is salved by the lilting, poignant beauty of the melody. The empathy of her delivery provides the greatest confirmation of why Sinéad O'Connor remains a vital force in contemporary music.